One of the items characteristically refurbished on a submarine during its periodic shipyard overhaul are it's circular hatches. These hatches normally contain about twelve tapered lugs around the hatch opening. It is necessary that these lugs be refurbished in order to make precision contact with the locking ring contained in the hatch cover. During refurbishment these tapered lugs must be worked until there is metal to metal blued contact between the lug and the ring in the hatch cover. Because of the wear to the lugs, clad welding is built up on each lug so that the lugs can then be machined to the proper mating surface with the hatch ring. In the past these lugs have been hand ground with a hand held air grinder. This method of repair is very inaccurate and invariably results in uneven and incorrect tapered angles on the lugs. Because of hand grinding mistakes the lugs often have to be recladded for another try at hand grinding. The inaccuracies which result are blended together by lapping with the locking ring. Unfortunately this method changes the machined angle on the locking ring necessitating its removal and its remachining to the correct angle in a machine shop. To lap the lugs by this method requires removal of the locking ring several times for remachining. The lapping procedure requires days of repetitious and tedious hatch closing, lapping by locking the hatch, opening, cleaning the lapping compound away, reapplying the lapping compound, and lapping again by locking the hatch.